Blog Car Care Advice What is Adblue DEF and Why Do Diesel Cars Need It?
Car Care Advice

What is Adblue DEF and Why Do Diesel Cars Need It?

Looking for a mechanic near you for maintenance or repair? AutoNation Mobile Service brings the shop to you. Get a free instant quote today.
Get a Quote

AdBlue is a diesel exhaust fluid that reduces harmful emissions from diesel engines and paves the way for cleaner transport. That’s why modern diesel vehicles are fitted with an Adblue warning light, which notifies you when you’re running low on this essential fluid. 

Join us as we delve into the depths of AdBlue and explore its significance.

This Article Contains:

Let’s get started.

What Is AdBlue?

AdBlue is a diesel exhaust fluid mainly used in commercial vehicles with a diesel engine. 

The fluid is added to pollutant control technology called the Selective Catalytic Reduction or SCR system fitted in your diesel vehicle. The fluid helps reduce harmful nitrogen oxide emissions (NOx emissions) in the exhaust gas through this system.

Why is reducing harmful exhaust emissions necessary?
Beyond helping the environment, the automotive industry must comply with a set of regulations known as Euro 6, which aims to reduce the nitrogen oxide emissions of a diesel car. 

As such, AdBlue fluid is an elegant solution for any vehicle manufacturer trying to comply with Euro 6 regulations. The fluid is injected into the exhaust gas and burnt at high temperatures to break down harmful nitrogen oxide compounds.

Now that we know what this diesel exhaust fluid is, let’s explore its composition. 

What Is AdBlue Made From?

AdBlue typically comprises 32.5% urea and 67.5% deionized water. This specific urea-water mixture enables the SCR system to efficiently reduce NOx emissions. 

Here’s how it’s made:
Manufacturers combine ammonia and carbon dioxide to create urea crystals under high pressure and temperature. They then dissolve the crystals in water to make the AdBlue fluid.

Next, let’s dive deeper into how AdBlue affects modern diesel cars.

How Does AdBlue Work?

AdBlue is pivotal in reducing nitrogen oxide emissions in the SCR system, and a diesel engine requires a good amount of it to function well. Typically, a diesel vehicle with SCR technology has a separate tank for AdBlue.

Here’s what Adblue does:

1. AdBlue moves from this diesel exhaust fluid tank (DEF tank) to the exhaust pipe in front of the SCR catalyst.

2. The exhaust pipe heat breaks down the fluid into ammonia and carbon dioxide. 

3. The nitrogen oxide emissions in exhaust gas react with the ammonia due to the presence of a catalyst

4. The harmful NOx emission in the exhaust system is then converted to harmless nitrogen and water, and these clean exhaust emissions are released as steam.

But here’s the thing:
If the amount of AdBlue is too low, the SCR system may not be able to convert enough harmful NOx emission. Conversely, a high amount of AdBlue may cause adverse effects on the SCR system, possibly damaging its components. It’s essential to use the correct quantity of AdBlue to ensure the proper functioning of a diesel car equipped with SCR technology.

As you can tell, AdBlue is cutting-edge technology in the fight against harmful nitrogen oxide emissions. 

But can you fit this essential fluid into your budget?
Let’s find out.

How Much Does AdBlue Cost?

AdBlue is relatively cheap, especially compared to other fluids that your vehicle requires, like diesel fuel and engine oil. But the price may vary, depending on the cost of urea production.

Generally, a 2.0-liter bottle of AdBlue may cost up to $30. At the same time, a 10-liter bottle may be worth just $32.50 since it’s cheaper to buy larger quantities, which are harder to store. Moreover, the AdBlue consumption of modern diesel cars isn’t too high, so you get more bang for your buck. 

According to the German Association of the Automotive Industry (Automotive Industry VDA), the average passenger car uses about a liter of AdBlue for every 1000km your vehicle travels. So, the separate tank is big enough for the diesel exhaust fluid to last between scheduled maintenance intervals, where mechanics would top it up. But you can top it up yourself if it’s running low and you see the DEF warning light activated on your dash. 

What Does the DEF Light Mean?

The DEF warning light, also known as the AdBlue warning light, is an indicator that appears on the dashboard of vehicles equipped with a diesel engine and SCR technology.

When the DEF warning light illuminates, it signals that the level of diesel exhaust fluid in the vehicle’s reservoir is getting low or has depleted. The warning light generally alerts you at around 1,500 miles from running out, which gives you plenty of time to refill your DEF tank.

Replenishing your AdBlue isn’t rocket science, but it does require some know-how.

Where to Buy AdBlue and How to Refill It

You can purchase a bottle of Adblue from garages, service stations, supermarkets, online retailers, and other automotive stores.

To refill the AdBlue tank yourself, you must find it first. It’s typically located behind the diesel fuel tank and has a blue cap. However, its location can vary depending on whether you own a heavy vehicle or a passenger car. The DEF tank is much smaller than the diesel tank and has marks confirming the amount of diesel exhaust fluid required. Just pour the bottle of AdBlue into the tank, and you’re ready to go.

Alternatively, you can refill AdBlue at most fuel stations with an AdBlue pump. Place the nozzle of the AdBlue pump in the Adblue tank and add the necessary amount. If you’re new to this, consult your owner’s manual to ensure you add the correct quantity and don’t accidentally add AdBlue to the diesel tank.  

Still on the fence?
Let’s discuss some common queries about this solution.

3 FAQs about AdBlue

Here are answers to commonly asked questions about AdBlue diesel exhaust fluid:

1. Which Cars Use AdBlue?

Due to strict Euro 6 emissions regulations, most diesel vehicles have been fitted with an AdBlue tank and a diesel particulate filter. In particular, diesel engines with over 1.6 liters capacity generally have AdBlue technology. 

Moreover, diesel vehicle manufacturers, such as Volkswagen, Audi, Mercedes, and Land Rover, must comply with environmental regulations in various countries. That’s why they’re making vehicles that utilize AdBlue and a diesel particulate filter to create harmless nitrogen.

2. Does AdBlue Affect Fuel Consumption?

While some DEF manufacturers claim DEF leads to reduced fuel consumption, there’s no evidence that AdBlue affects your car’s fuel tank or mileage. That said, no vehicle manufacturer has released credible data that claims that diesel exhaust fluid has any adverse impact on fuel consumption. 

3. Is AdBlue Hazardous?

No, AdBlue isn’t hazardous. Urea, the base of the fluid, occurs naturally in the human body, so it’s not wildly harmful. However, you should never ingest or inhale the fluid as it’s corrosive. To ensure your safety, you should use gloves when dealing with AdBlue.  

Final Thoughts

AdBlue has become a necessity to help reduce harmful emissions from a diesel vehicle. And while AdBlue offers significant benefits, it does require proper handling. So, following vehicle manufacturer guidelines and refilling your AdBlue tank regularly is crucial. 

Looking for a reliable auto service that can help you maintain your diesel engines?

AutoNation Mobile Service offers top-quality auto repair and maintenance by expert mechanics who’ll do the work right from your driveway. Plus, you’ll benefit from upfront pricing and a service warranty.

Fill out this form to fix an appointment for an AdBlue refill or any other car maintenance procedures!